Optimized edge order for de-blocking filter

ABSTRACT

A de-blocking filter includes a reconstructed memory that is configured to store reconstructed pixels corresponding to a current macroblock of a video image to be filtered. The current macroblock includes a set of sub-blocks, each sub-block having horizontal edges and vertical edges. An internal pixel buffer in the de-blocking filter is configured to store pixels corresponding to the set of sub-blocks from the reconstructed memory, and to store partially filtered pixels corresponding to a set of partially filtered macroblocks. An edge order controller in the de-blocking filter is configured to load the pixels corresponding to the set of sub-blocks into a filter engine from the internal pixel buffer, to filter the set of sub-blocks, such that, at least one horizontal edge is filtered before filtering all vertical edges of the set of sub-blocks.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/278,697, filed May 15, 2014, which claims priority from Indian patentapplication No. 2133/CHE/2013 filed on May 15, 2013, both of which arehereby incorporated by reference in their entirety.

TECHNICAL FIELD

Embodiments of the disclosure relate to de-blocking filter in a videoprocessor.

BACKGROUND

Transformation and quantization in block based video codecs introducesblocking artifacts at edges. Special optimized video filter calledde-blocking filter is conditionally applied on 4×4/8×8 pixel blockboundary to enhance visual quality and improve prediction efficiency.Most of the recent video codecs such as H.264, H.265 (HEVC), and VC-1uses in-loop de-blocking filter in the decoder path. Each video codecstandard defines fixed order of filter operation to have consistency inuniversal decoder output.

Standard defined fixed edge order is not optimal for variousarchitectures of de-blocking filter hardware accelerator (HWA), as itwill have to compromise on performance, power or area. In-loopde-blocking filter integrated in video processing engine running atmacroblock (MB) level pipeline is challenging in handling MB boundarylevel pixels. Concurrent operation of loading and storing of unfiltered,partially filtered and fully filtered pixels in and out of the internalstorage along with the filter operation are some of the challenges thatare difficult to meet with standard defined edge order for filteroperation without getting impacted due to stall from shared memoryaccess.

SUMMARY

This Summary is provided to comply with 37 C.F.R. § 1.73, requiring asummary of the invention briefly indicating the nature and substance ofthe invention. It is submitted with the understanding that it will notbe used to interpret or limit the scope or meaning of the claims.

An embodiment provides a de-blocking filter in a video processor. Thede-blocking filter includes a reconstructed memory that is configured tostore reconstructed pixels corresponding to a current macroblock of avideo image to be filtered. The current macroblock includes a set ofsub-blocks, each sub-block having horizontal edges and vertical edgeshaving a left vertical edge, a right vertical edge, a top horizontaledge and a bottom horizontal edge. The de-blocking filter furtherincludes an internal pixel buffer configured to store pixelscorresponding to the set of sub-blocks from the reconstructed memory,and to store partially filtered pixels corresponding to a set ofpartially filtered macroblocks. An edge order controller in thede-blocking filter is configured to load the pixels corresponding to theset of sub-blocks into a filter engine from the internal pixel buffer,to filter the set of sub-blocks, such that, at least one horizontal edgeis filtered before filtering all vertical edges of the set ofsub-blocks.

Another embodiment provides a method for de-blocking filtering in avideo processor. Pixels corresponding to a set of sub-blocks of acurrent macro-block of a video image to be filtered are loaded first.Then, partially filtered pixels corresponding to a set of partiallyfiltered macroblocks and a set of filter parameters are loaded. The setof sub-blocks are then filtered, such that, at least one horizontal edgeis filtered before filtering all vertical edges of the set ofsub-blocks.

Another embodiment provides a method for de-blocking filtering in avideo processor. Pixels corresponding to a set of sub-blocks of acurrent macro-block of a video image to be filtered are loaded first.Then, partially filtered pixels corresponding to a set of partiallyfiltered macroblocks and a set of filter parameters are loaded. The setof sub-blocks are then filtered, such that at least one horizontal edgeis filtered before filtering all vertical edges of the set ofsub-blocks; the set of sub-blocks are processed from top to bottom ofthe macroblock, and such that a filtering order for each sub-block isthe left vertical edge followed by the right vertical edge followed bythe top horizontal edge and followed by the bottom horizontal edge;filtering any two edges of the sub-block is separated at least by onecycle of the de-blocking filter; and the vertical left edge and thevertical right edge of a bottom vertical sub-block is filtered beforefiltering a horizontal edge between two vertical sub-blocks of the setof sub-blocks.

Another embodiment provides a de-blocking filter in a video processor.The de-blocking filter includes a reconstructed memory that isconfigured to store reconstructed pixels corresponding to a currentmacroblock of a video image to be filtered. The current macroblockincludes a set of sub-blocks, each sub-block having horizontal edges andvertical edges having a left vertical edge, a right vertical edge, a tophorizontal edge and a bottom horizontal edge. The de-blocking filterfurther includes an internal pixel buffer configured to store pixelscorresponding to the set of sub-blocks from the reconstructed memory,and to store partially filtered pixels corresponding to a set ofpartially filtered macroblocks. An edge order controller in thede-blocking filter is configured to load the pixels corresponding to theset of sub-blocks into a filter engine from the internal pixel buffer,to filter the set of sub-blocks, such that, at least one horizontal edgeis filtered before filtering all vertical edges of the set ofsub-blocks; a filtering order for each sub-block is the left verticaledge followed by the right vertical edge followed by the top horizontaledge and followed by the bottom horizontal edge, such that, the set ofsub-blocks are processed from top to bottom of the current macroblock;filtering any two edges of the sub-block is separated at least by onecycle of the de-blocking filter; and the vertical left edge and thevertical right edge of a bottom vertical sub-block is filtered beforefiltering a horizontal edge between two vertical sub-blocks of the setof sub-blocks.

Other aspects and example embodiments are provided in the Drawings andthe Detailed Description that follows.

BRIEF DESCRIPTION OF THE VIEWS OF DRAWINGS

FIGS. 1a and 1b illustrate a standard edge order filter operation;

FIG. 2a illustrates a customized edge order filter operation accordingto an embodiment;

FIG. 2b illustrates a customized edge order filter operation accordingto another embodiment;

FIG. 3a is a block diagram of a deblocking filter in the video processoraccording to an embodiment;

FIG. 3b is a block diagram of the deblocking filter according to anembodiment;

FIG. 4 is a flowchart illustrating the customized filter order operationaccording to an embodiment; and

FIG. 5 is an example environment in which various aspect of the presentdisclosure can be implemented.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A de-blocking filter is used in video codecs, i.e. H.264 AVC/SVC, H.265,VC-1 etc., to improve subjective video quality and to enhance quality ofbit stream encoding. FIGS. 1(a) and 1(b) illustrate a standard edgeorder de-blocking filter operation in H.264 video processing. Neighborpixel aware adaptability of the de-blocking filter operation, loading ofunfiltered/partially filtered pixels and storing of fully/partiallyfiltered pixels for a given standard defined edge order of filteroperation increases complexity of overall de-blocking filter for highperformance video processing engine. To illustrate the complexity, astandard edge order filter operation is illustrated in FIG. 1a . A 16×16macroblock is shown in FIG. 1a having a set of sub-blocks, for examplesub-block 118. Each column of sub-blocks of the macroblock has verticaledges 102, 104, 106, 108 and row of sub-blocks of macroblock hashorizontal edges 110, 112, 114 and 116. For example sub-block 118 has aleft vertical edge 120, a right vertical edge 122, a top horizontal edge124 and a bottom horizontal edge 126.

The standard edge order filter operation, such as for H.264 standarddefined edge order is defined as vertical edges 102, 104, 106, 108 fromleft to right followed by horizontal edges 110, 112, 114 and 116 fromtop to bottom as shown in FIG. 1a . Such a filter order is furtherillustrated in FIG. 1b . A 16×16 current macroblock 128 is illustratedalong with a left macroblock 130 and upper macroblock 132. The numbers0-31 shown on each edge of the sub-blocks indicate the correspondingcycle of the de-blocking filter.

There are generally five stages in a de-blocking filter operation. A setof parameters are loaded (for example filter parameters, controlparameters, macroblock parameters etc.) followed by computing filterstrength for each edge (called boundary strength). Then pixelscorresponding to the current macroblock and partially filtered neighbormacroblocks are loaded. The current macroblock is filtered thereafterand pixels corresponding to partially filtered sub-blocks and fullyfiltered sub-blocks of the left macroblock, upper macroblock and currentmacroblock are stored. Loading, filtering and storing operations arerepeated for luma (Y) and chroma (Cb and Cr). Standard defined order offilter operation of sub-block of the macroblock is as illustrated inFIG. 1 b.

From the foregoing discussion, it is clear that pixels corresponding toa particular sub-block needs to be loaded and stored in a storage tillall the four edges of that particular sub-block is filtered. In theexample of FIG. 1b , pixels corresponding to the sub-block C0 need to bestored till 20^(th) cycle of the de-blocking filter because the bottomhorizontal edge of sub-block C0 (134) is filtered only in 21^(st) cycleof the de-blocking filter. Further, pixels corresponding to the leftmacroblock 130 (right vertical edges of the sub-blocks of leftmacroblock) and upper macroblock 132 (bottom horizontal edges of theupper macroblock) also need to be loaded and stored while filtering thecurrent macroblock 128. This increases the storage requirement in thearchitecture. For an edge filter order of FIG. 1b , pixels correspondingto the full 16×16 current macroblock needs to be stored duringfiltering. It can also be noted that the fully filtered pixels write isnot properly staggered across full filter operation that leads to stallsin filter operation. Further, the reconstructed pixels corresponding tothe current macroblock needs to be loaded sequentially. All 16 luma 4×4blocks for the current macroblock needs to be loaded for consecutive 16cycles. This leads to stall on loading pixels during filter operation.For a standard defined edge order filter operation as in FIG. 1b , theperformance measurement for an un-pipelined de-blocking filter wasestimated to take 632 cycles of the de-blocking filter for standardvideo processing architecture. Even after including other enhancementwithout optimizing efficient load/store from shared memories and filteroperation, reaching better than 200 cycle is difficult. For a highperformance de-blocking filter which helps in reaching 4K 60 fps or 4channels of 1080P 60 fps performance, standard defined edge orderinvariably creates problem in pixel loading/storage and becomesbottleneck in creating efficient pipelined architecture.

A customized edge order filter operation is illustrated in FIGS. 2a and2b that overcomes the disadvantages associated with a standard definededge order filter operation, according to an embodiment. The fundamentalcondition to the customized edge order filter operation is that at leastone horizontal edge is filtered before filtering all vertical edges 102,104, 106, 108 of the set of sub-blocks. Another condition is thatfiltering of any two edges of the sub-block is separated at least by onecycle of the de-blocking filter. Customized edge order as in FIG. 2a isused when a same sub-block is available for its another edge filteroperation after 2 cycles, whereas in FIG. 2b is used when same sub-blockis available for its another edge filter operation after 1 cycle.

Referring now to FIG. 2a , a current macroblock 202, left macroblock 204and upper macroblock 206 of a video image are illustrated. The indexes0-31 shown on each edge of the set of sub-blocks (C0-C15) indicate thecorresponding cycle of the de-blocking filter. Each sub-block is of 4×4pixel size. The customized edge order filter operation according to oneembodiment, is implemented such that any two edges of the sub-block, forexample sub-block C0, is separated at least by two cycle of thede-blocking filter. It can be noted that the top horizontal edge andright vertical edge of the sub-block C0 is filtered at cycles 4 and 2 ofthe de-blocking filter respectively and are separated by two cycles. Forthe purpose of explaining the customized filter edge order of FIGS. 2aand 2b , it is considered that the first cycle count for the de-blockingfilter starts from cycle 0, which is the left vertical edge of sub-blockC0. It can also be noted that the sub-block C0 is fully filtered within7 cycles of the de-blocking filter. The set of sub-blocks are processedfrom top to bottom of the current macroblock 202 according to thisembodiment as illustrated in FIG. 2a . For example, the verticalneighboring sub-blocks C0, C2 and C8 are filtered within 7, 10 and 13cycles of the de-blocking filter. A filtering order for each sub-blockis the left vertical edge followed by the right vertical edge followedby the top horizontal edge and followed by the bottom horizontal edge,such that, the set of sub-blocks are processed from top to bottom of thecurrent macroblock. It is also noted that the left vertical edge and theright vertical edge of a bottom vertical neighbor sub-block is filteredbefore filtering a horizontal edge between a current sub-block and thebottom vertical neighbor sub-block. Taking an example of sub-blocks C0and C2, and considering C2 as the bottom vertical neighbor sub-block andC0 as the current sub-block, it can be seen that left vertical edge (incycle 2) and the right vertical edge (in cycle 4) of a bottom verticalneighbor sub-block (C2) is filtered before filtering a horizontal edge(in cycle 7) between a current sub-block and the bottom verticalneighbor sub-block.

FIG. 2b illustrates another embodiment of customized edge order filteroperation where any two edges of the sub-blocks are separated at leastby one cycle of the de-blocking filter and a current macroblock 208,left macroblock 212 and upper macroblock 210 of a video image areillustrated. The indexes 0-31 shown on each edge of the set ofsub-blocks (C0-C15) indicate the corresponding cycle of the de-blockingfilter. Each sub-block is of 4×4 pixel size. The customized edge orderfilter operation according to one embodiment, is implemented such thatany two edges of the sub-block, for example sub-block C0, is separatedat least by one cycle of the de-blocking filter. It can be noted thatthe top horizontal edge and right vertical edge of the sub-block C0 isfiltered at cycles 3 and 2 of the de-blocking filter respectively andare separated by one cycle. It can also be noted that the sub-block C0is fully filtered within 6 cycles of the de-blocking filter. The set ofsub-blocks are processed from top to bottom of the current macroblock208 according to this embodiment as illustrated in FIG. 2b . Forexample, the sub-blocks C0, C2 and C8 are filtered, which are thevertical neighboring sub-blocks, within 6, 9 and 12 cycles of thede-blocking filter. A filtering order for each sub-block is the leftvertical edge followed by the right vertical edge followed by the tophorizontal edge and followed by the bottom horizontal edge, such that,the set of sub-blocks are processed from top to bottom of the currentmacroblock. It is also noted that the left vertical edge and the rightvertical edge of a bottom vertical neighbor sub-block is filtered beforefiltering a horizontal edge between a current sub-block and the bottomvertical neighbor sub-block. Taking an example of sub-blocks C0 and C2,and considering C2 as the bottom vertical neighbor sub-block and C0 asthe current sub-block, it is seen that left vertical edge (in cycle 4)and the right vertical edge (in cycle 5) of a bottom vertical neighborsub-block (C2) is filtered before filtering a horizontal edge (in cycle6) between a current sub-block and the bottom vertical neighborsub-block.

The effect of customized edge order filter operations of FIGS. 2a and 2bon the de-blocking filter architecture is explained using de-blockingfilter integrated within video processor as shown in FIG. 3a and thede-blocking filter block diagram of FIG. 3b . The de-blocking filter ofFIG. 3b is illustrated as a part of a video processing processor withother interfacing blocks as shown in FIG. 3a . The video processor mayhave other blocks which are not shown for the brevity of explanation.

The video processor includes various functional blocks for encoding anddecoding of video data. The video processor configured to work asdecoder, receives bit-stream for video decoding. An Entropy Decoder(ECD) (not shown in FIG. 3a ) extracts motion vector information,macroblock coding parameters and quantized and transformed predictionerror besides other encoded parameters useful for video decode. A MotionCompensation (MC) block (not shown in FIG. 3a ) loads set of blocks fromreference frame as required by motion vector and prediction informationreceived by ECD. MC block creates predicted macroblock for furtherprocessing by quantization and transformation block (CALC) 330. The CALC330 inverse quantize and inverse transform received prediction error andrecreate macroblock after adding with predicted MB generated by MC. Thisrecreated pixels of macroblock, called reconstructed pixels, is filteredby de-blocking filter 326 to eliminate blocking artifacts. Fullyfiltered decoded frame is stored back into external memory (not shown inFIG. 3a ) for display or any post processing operation.

Video processor configured to work as encoder, receives video frame fromeither camera source or external storage with set of video frame data.Received frame is processed in unit of macroblock. Intra predictionblock and Motion Estimation Engine (MEE) (not shown in FIG. 3a )estimates best prediction type of received macroblock and generatespredicted motion vector if prediction type is inter macroblock. Theintra prediction block and motion estimation engine creates a predictedMB, if inter-MB, based on received motion vector. CALC 330 generatesprediction error based on predicted and received MB and pass onprediction error to entropy coder (ECD) after transformation andquantization. The ECD generates encoded bit-stream after entropy codingof received data from CALC along with encoding of motion vectorprediction error and other relevant prediction and coding parameters.CALC 330 already having predicted MB also does reverse quantization andreverse transformation on prediction error, as it does in the decoder,to recreate reconstructed pixel like on generated bit stream.Reconstructed pixel is filtered by de-blocking filter 326 to eliminateblocking artifacts. Fully filtered decoded frame is stored back intoexternal memory (not shown in FIG. 3a ) to be used as reference for nextframe encoding.

Video processor operable as encoding or decoding engine has commonde-blocking filter block 326 as in FIG. 3a . Central processing unit(CPU) 328 provides operable parameters to de-blocking block 326 throughconfiguration interface. These parameters includes, but not limited to,enabling the de-blocking operation and various address pointers of pixeland parameter buffer in shared memory (SL2 memory) 332. Reconstructedpixels to de-block filtered is generated by quantization andtransformation block (CALC) 330. CALC 330 generates reconstructed pixelsand pass onto de-blocking filter 326. De-blocking filter 326 receivesconfiguration parameters from CPU 328, reconstructed pixels andavailable de-blocking and MB/slice parameter from CALC 330 and restother parameters from SL2 memory 332 not available inside CALC 330.De-blocking filter 326 also receives partially filtered pixels of uppermacroblock from SL2 memory 332 and store back fully filtered currentmacroblock and partially filtered bottom pixels in SL2 memory 332. Inanother embodiment CALC 330 writes reconstructed pixels and availablede-blocking and MB/slice parameters into shared memory 330 andde-blocking filter 326 loads them as required during filter operation.

FIG. 3b illustrates the de-blocking filter (326) operable to eliminateblocking artifacts due to block based video processing. The de-blockingfilter includes a configuration interface 302 connected to a MemoryMapped Register (MMR) 304. The configuration interface 302 is MMRconfiguration interface connected directly or through interconnect toCPU or anything similar to an initiator capable of accessing the MMR304. The MMR 304 is required to store configured control parameters forthe filter operation. The MMR 304 includes all information regardingpre-filter data loading parameters as well as post filter data storageparameters. An output of the MMR 304 is connected to de-block parameterstorage 306. The de-block parameter storage 306 is configured to storecontrol parameters for filtering the current macroblock. This includesruntime parameters as well as configured parameters through theconfiguration interface 302 and passed on to the MMR 304. A set ofruntime macroblock/slice level parameters are also loaded by acontroller 312 from a shared memory (SL2 memory) 324 and stored into thede-block parameter storage 306. In another embodiment themacroblock/slice level parameters are passed on by previous stage CALCHWA along with reconstructed pixels. A reconstructed controller 308loads these parameters from reconstructed memory 310 and store intode-block parameter storage 306 after starting filter operation.

The reconstructed controller 308 is configured to control writing ofreconstructed pixels along with macroblock/slice level parameters intothe reconstructed memory 310. The reconstructed controller 308 alsoinforms the controller 312 about availability of reconstructed pixels.After the controller 312 starts the filter operation, the reconstructedcontroller 308 loads parameters from reconstructed memory 310 and storesinto de-block parameter storage 306. The reconstructed controller 308 isalso controlled by edge order controller 314 as part of controller 312to load reconstructed pixels from the reconstructed memory 310 and storeinto an internal pixel buffer 318. The reconstructed memory 310 isconfigured to store reconstructed pixels corresponding to the currentmacroblock of the video image to be filtered.

An edge order controller 314 in a controller 312 is coupled to thede-block parameter storage 306, the reconstructed controller 308, an SL2memory 324 via SL2 memory interface 322 and a left memory 320 to managesequencing of data load from these as per their requirement in filteroperation. The controller 312 controls starting the de-blocking filteroperation, sequencing luma(Y) and chroma (Cb and Cr) filter operationand indicating end of filter operation. An edge order controller 314manages order of the filter operation as per customized edge order,managing loading of various partially/non-filtered pixels from thereconstructed memory 310, the SL2 memory 324 and the left memory 320.The edge order controller 314 being part of controller 312 is connectedto a filter engine 316. The filter engine 316 applies filter operationon every filterable edge of both luma and chroma components. Filterengine has 4 independent H.264 filter blocks and operates on all 4-pixelsets of 4×4 sub-blocks in parallel. Filtering is performed based oncomputed boundary strength (BS) for each edge and on otherslice/macroblock parameters (disable_de-blocking_ filter_idc,picture/frame boundary, slice boundary etc.). In another embodiment,controller 312 contains all the functionality of edge order controller314. Its connectivity with rest of blocks remains same.

The filter engine 316 is connected to an internal pixel buffer 318. Theinternal pixel buffer 318 is configured to store pixels corresponding tothe set of sub-blocks from the reconstructed memory 310, and to storepartially filtered pixels corresponding to a set of partially filteredmacroblocks. The internal pixel buffer 318 stores pre-filter 4×4 pixeldata and runtime partially filtered data. Data is sourced fromreconstructed memory 310, the SL2 memory 324 and the left memory 320 andeventually stored back into the SL2 memory 324 and the left memory 320.In another embodiment, the left memory 320 or any other internal storagecan be extended to store all post processed pixels (filter/partiallyfiltered). In another embodiment content of reconstructed memory can bewritten by CALC in SL2 memory 324 and loaded by edge order controller314 through SL2 memory interface 322.

Generally, the requirement in the de-blocking filter operation is tominimize storage and stay of pixels in internal pixel buffer 318corresponding to sub-blocks such that filter engines (in case of a 4×4sub-block) are never stalled due to lack of Internal Pixel Bufferstorage (IPB) 318. All load and store operation happens in backgroundexcept at the beginning and end of the filter operation. Also resultantfiltered data must be bit-exact to standard defined edge order filteroperation. Customized edge order illustrated in FIGS. 2a and 2b ,according to an embodiment overcomes storage and performance bottleneckof standard edge order filter operation.

H.264 filter operation has two parts. First part, called a pre-filteroperation, is computation of α β and tc₀ and second part is BoundaryStrength (BS) dependent filter operation. Sequencing both operations insingle cycle timing path for 266 MHz de-blocking filter engine is timingcritical. Filter engine 316 filters sub-blocks loaded from internalpixel buffer 318 and stores back processed sub-block into internal pixelbuffer 318. One pipeline stage has been added in filter operation, afterpre-filter stage, to eliminate timing pressure on path between filterengine 316 and internal pixel buffer 318. This creates problem for edgeorder selection, as same 4×4 sub-blocks is not required for filteroperation back-to-back. Either it will create bubble/idle-cycle insidefilter operation or filter output will be required to be fed throughinto pre-filter pipeline stage. Both design constraints are avoidable ifminimum 2-cycle gap is assumed between edges of same 4×4 blocks such asthe one illustrated in FIG. 2 a.

In another embodiment, pre-filter operation and filter operation can becompleted in single cycle. Operation includes loading sub-blocks frominternal pixel buffer 318, filter operation and store back filteredsub-blocks in internal pixel buffer 318. This eliminates need of twocycle gap. With one cycle gap between two edges of sub-block, thecustomized edge order is as illustrated in FIG. 2 b.

The left memory 320 is configured to store pixels corresponding to apartially filtered left macroblock of the set of partially filteredmacroblocks. This includes partially filtered right 4×4 block column ofluma, Cb and Cr to be used in next macroblock filtering (filtercandidate macroblock is always in faster scan order). The left memory320 also serves as temporary storage, for example, MBAFF (macroblockadaptive frame or filed coding) frame pair upper macroblock bottom rowstorage, fully filtered current macroblock Cb components beforeinterleaving with Cr components for writing in NV12 format output.

Shared Memory (SL2) interface unit 322, coupled to the controller 312,SL2 memory 324 and the internal pixel buffer 318, is configured to loadpartially filtered pixels and required macroblock/slice parameters fromthe SL2 memory 324. The SL2 memory 324 is configured to store pixelscorresponding to a partially filtered upper macroblock of the set ofpartially filtered macroblocks and a set of parameters corresponding tothe partially filtered upper macroblock. The SL2 memory interface 322also assists in writing fully filtered pixels and partially filterbottom row into the SL2 memory 324. The SL2 memory interface also loadsCb from the left memory 320 prior to Cb and Cr interleaving andeventually writing into fully filtered chroma buffer in SL2 memory 324.In another embodiment SL2 memory interface 322 also helps in loadingreconstructed pixels and all MB/slice parameters from SL2 memory 324.

Shared memory (SL2) 324 is shared by all HWAs of the video processor.Its access interface is stallable for de-blocking filter. Systemperformance has shown that probability of stalling each SL2 memory 324access is 20%. Said differently, one access out of 5 accesses can bestalled. The customized edge order filtering, according to severalembodiments, need 40 SL2 access for loading and storing pixels. Evenlydistributed accesses have more chance of absorbing stall thanback-to-back access. With customized edge order of FIGS. 2a and 2b , SL2writes are well sparse throughout filter operation window and makes thedesign more robust against SL2 stall. In another embodiment SL2 memory324 can be used for storing and loading all data required forde-blocking filter operation.

The filter engine 316 is controlled by the edge order controller 314 tofilter the set of sub-blocks based on several conditions as explainedbelow. One condition, according to an embodiment is that, at least onehorizontal edge is filtered before filtering all vertical edges of theset of sub-blocks. Second condition is that a filtering order for eachsub-block is the left vertical edge followed by the right vertical edgefollowed by the top horizontal edge and followed by the bottomhorizontal edge, such that, the set of sub-blocks are processed from topto bottom of the current macroblock (202 or 208). Third condition isthat filtering any two edges of the sub-block is separated at least byone cycle of the de-blocking filter. Examples of any two edges of thesub-block being separated at least by two cycles and at least by onecycle of the de-blocking filter are illustrated in FIGS. 2a and 2b .Fourth condition is that the vertical left edge and the vertical rightedge of a bottom vertical sub-block is filtered before filtering ahorizontal edge between two vertical sub-blocks of the set ofsub-blocks.

It is noted that the pattern of output data of the de-blocking filter,in case of interlaced picture is key concern for a de-blockarchitecture. In case of MBAFF frame-pair and interlaced frame (PiCFF)mb, even and odd fields are may be required to be stored into separatefilter buffers in the SL2 memory 324. Two vertical neighbors 4×4 blocksare paired to generate separate even and odd 4×4 blocks in oneembodiment. This is possible only if the order of generation ofprocessed pixels is from top to bottom. For any other order of outputpixel generation, temporary storage required for pairing will increase.For the customized edge order filter, two different pairing storage onSL2 memory interface 322 is sufficient to meet performance. Standarddefined edge order will require minimum 4 such pairing storage, as orderof generated filtered pixels are from left to right (except the first4×16 column).

Customized edge order as illustrated in FIGS. 2a and 2b is for lumacomponent of macroblock. Chroma component in 4:2:0 is of size 8×8 andslight modification is required in edge order. Referring to FIG. 2 a,2-cycle gap required customized edge order for chroma will be 0, 1, 2,3, 4, 14, 6 and 16. Similarly referring FIG. 2 b, 1-cycle gap requiredcustomized edge order for chroma will be 0, 2, 4, 1, 3, 6, 14 and 16.Numbering as explained above is cycle number associated with edge incustomized edge order for luma.

Operation of the de-blocking filter in FIG. 3b is illustrated using theflowchart of FIG. 4 according to an embodiment.

At step 402 the availability of reconstructed pixels is checked. TheController 312 is informed by the reconstructed controller 308, when allreconstructed sub-blocks of macroblock is available in reconstructedmemory 310. At step 404, a set of control parameters for filtering acurrent macroblock are loaded. De-block parameters are written alongwith reconstructed pixels in the reconstructed memory 310. Reconstructedcontroller 308 loads these parameters, such as coding type, slice type,quantization parameter etc into de-block parameter storage 306.Controller loads some remaining parameters from shared memory 324 andstores into de-block parameter storage 306.

At step 406, pixels corresponding to a set of sub-blocks of the currentmacroblock are loaded. Reconstructed pixels are loaded into internalpixel buffer in a pre-defined order to be required for filter operationas per customized edge order.

At step 408, partially filtered pixels corresponding to a set ofpartially filtered macroblocks are loaded. There are three differentkinds of data required in the filter operation. Reconstructed pixelsstored in reconstructed memory, partially filtered pixels of leftmacroblock stored in left memory 320 and of upper macroblock stored inSL2 memory 324. Customized edge order needs fixed order of sub-blockloading from all three sources. This order can change for a change inedge order. Edge order controller 314 ensures to load requiredsub-blocks from sources into internal pixel buffer. It also handlesconflict of sub-blocks from different sources slated for storage intosame internal pixel buffer entry. Edge order controller 314 controlsloading the pair of sub-blocks into filter engine 316 as per customizededge order.

At step 410, the set of sub-blocks are filtered such that at least onehorizontal edge is filtered before filtering all vertical edges of theset of sub-blocks. After filter operation processed sub-blocks arestored back into internal pixel buffer. After all filterable edges of asub-block are filtered and stored back into either left memory(partially filtered pixel for partially filtered left macroblock) orinto SL2 memory (fully filtered pixels and partially filtered pixels forpartially filtered upper macroblock).

Step 406, 408 and 410 is repeated till all sub-blocks of macroblock arefully processed. In another embodiment, step 406, 408 and 410 operatesin parallel till all sub-blocks of macroblock is fully processed fromde-blocking filter. Various embodiments of the present disclosure areimplemented in video codecs such as H.264, H.265 (HEVC), and VC-1. Asper various embodiments IPB area is reduced by ˜38% for one suchimplementation for H.264. The IPB only needs to have storage for 10 4×4blocks. This also leads to savings in power reduction as smaller IPBleads to smaller mux sizes around IPB. Current MUX logic is 10:2 (128bmux) Vs 25:2 (128b mux). Further, staggered loading of partiallyfiltered top row pixels, helps in absorbing SL2 memory access stalls.Reconstructed memory loading stall can be better absorbed, as nextreconstructed pixel sub-block is not required back to back. Staggeredwrite of processed 4×4 blocks into SL2 memory make it more stalltolerant. All combined above helps in achieving 100 cycle de-blockingfilter requirement with lower area and lower power for 1080 240 fpsH.264 decode/encode enabler.

FIG. 5 is an example environment in which various aspect of the presentdisclosure may be implemented. As shown, the environment may comprise,for example, one or more video cameras 510, computers 520, PersonalDigital Assistants (PDA) 530, mobile devices 540, televisions 550, videoconference systems 560, video streaming systems 580, TV broadcastingsystems 570 and communication networks/channels 590.

The video cameras 510 are configured to take continuous pictures andgenerate digital video signal comprising sequence of image frames. Thevideo cameras 510 are configured to process the image frames forefficient storage and/or for transmission over the communication network590. The computers 520, PDAs 530 and the mobile devices 540 areconfigured to encode the video signals for transmission and to decodeencoded video signals received from the communication networks/channels590. The video streaming system 580 is configured to encode video signaland to transmit the encoded video signals over the communicationnetworks/channels 590 responsive to a received request and/orasynchronously. The television broadcast systems 570 are configured toprocess video signals in accordance with one or more broadcasttechnologies and to broadcast the processed video signals over thecommunication networks/channels 590. The video conference systems 160are configured to receive a video signal from one or moreparticipating/conferencing end-terminals (not shown) and to convert orcompress the video signal for broadcasting or for transmitting to otherparticipating user terminals. The televisions 550 are configured toreceive encoded video signals from one or more different broadcastingcenters (or channels), to decode each video signal and to display thedecoded video signals on a display device (not shown).

As shown in FIG. 5, the devices and systems 510-580 are coupled tocommunication networks/channels 590. Communication networks/channels 190supports an exchange of video signal encoded in accordance with one ormore video encoding standards such as, but not limited to, H. 263, H.264/AVC, and HEVC (H. 265), for example. Accordingly, the devices andsystems 510-580 are process (encode and/or decode) video signalscomplying with such standards. The systems and devices 510-580 areimplemented with one or more functional units that are configured toperform signal processing, transmitting and/or receiving of videosignals from communication networks/channels 590.

The foregoing description sets forth numerous specific details to conveya thorough understanding of the invention. However, it will be apparentto one skilled in the art that the invention may be practiced withoutthese specific details. Well-known features are sometimes not describedin detail in order to avoid obscuring the invention. Other variationsand embodiments are possible in light of above teachings, and it is thusintended that the scope of invention not be limited by this DetailedDescription, but only by the following Claims.

What is claimed is:
 1. A de-blocking filter in a video processorcomprising: a memory configured to store reconstructed pixelscorresponding to a macroblock of a video image to be filtered, themacroblock having a set of sub-blocks organized into columns, eachsub-block having horizontal edges and vertical edges comprising a leftvertical edge, a right vertical edge, a top horizontal edge and a bottomhorizontal edge; a filter controller configured to: filter the set ofsub-blocks to generate a set of fully filtered sub-blocks in part byfiltering either the top horizontal edge or the bottom horizontal edgebefore filtering the left vertical edge and the right vertical edge,wherein the left vertical edge, the right vertical edge, the tophorizontal edge, and the bottom horizontal edge each corresponds to adifferent cycle of the de-blocking filter, and wherein, for each of thecolumns of the sub-blocks, filtering for all sub- blocks in therespective column is completed prior to completing filtering for anycolumn of sub- blocks to the right of the respective column.
 2. Thede-blocking filter of claim 1 and further comprising: a left memoryconfigured to store pixels corresponding to a partially filtered leftmacroblock of the set of partially filtered macroblocks; an SL2 memoryconfigured to store pixels corresponding to a partially filtered uppermacroblock of the set of partially filtered macroblocks and a set ofparameters corresponding to the partially filtered upper macroblock; anda de-block parameter storage configured to store control parameters forfiltering the macroblock.
 3. The de-blocking filter of claim 1, whereinthe filter controller is configured to filter the set of sub-blocks,such that, filtering of any two edges of the sub-block is separated atleast by one cycle of the de-blocking filter.
 4. The de-blocking filterof claim 1, wherein a filtering order for each sub-block is the leftvertical edge followed by the right vertical edge followed by the tophorizontal edge and followed by the bottom horizontal edge, such that,the set of sub-blocks are processed from top to bottom of themacroblock.
 5. The de-blocking filter of claim 3, wherein the filtercontroller is configured to filter the set of sub-blocks, such that, theleft vertical edge and the right vertical edge of a bottom verticalneighbor sub-block is filtered before filtering a horizontal edgebetween a sub-block and the bottom vertical neighbor sub-block of theset of sub-blocks.
 6. The de-blocking filter of claim 1, furthercomprising an internal pixel buffer configured to store pixelscorresponding to the set of fully filtered sub-blocks of the macroblock.7. The de-blocking filter of claim 6, wherein the internal pixel bufferis configured to reduce storage of partially filtered pixels and fullyfiltered pixels corresponding to the set of sub-blocks.
 8. Thede-blocking filter of claim 1, wherein the macroblock is of a 16×16pixel size and each sub-block is of a 4×4 pixel size.
 9. The de-blockingfilter of claim 8, wherein the filter controller comprises four conpixel filters corresponding to each pixel edge between two neighboringsub-blocks of the set of sub-blocks.
 10. A method for de-blockingfiltering in a video processor, comprising: loading pixels correspondingto a set of sub-blocks of a macroblock of a video image to be filtered,the sub-blocks being organized in columns, each sub-block havinghorizontal edges and vertical edges comprising a left vertical edge, aright vertical edge, a top horizontal edge and a bottom horizontal edge;filtering the set of sub-blocks such that at least one horizontal edgeis filtered before filtering all vertical edges of the set ofsub-blocks, such that each of the horizontal and vertical edgescorresponds to a different cycle of the de-blocking filter, and suchthat for each of the columns of the sub-blocks, filtering for allsub-blocks in the respective column is completed prior to completingfiltering of any sub-blocks for any columns to the right of therespective column.
 11. The method of claim 10, wherein prior to loadingpixels corresponding to the set of sub-blocks: checking if reconstructedpixels corresponding to the macroblock are available.
 12. The method ofclaim 10, further comprising loading partially filtered pixelscorresponding to the partially filtered macroblock.
 13. The method ofclaim 10 further comprising: storing pixels corresponding to a set offully filtered sub-blocks.
 14. The method of claim 10, wherein filteringthe set of sub-blocks comprises: filtering order the left vertical edgefollowed by the right vertical edge followed by the top horizontal edgeand followed by the bottom horizontal edge, such that, the set ofsub-blocks are processed from top to bottom of the macroblock.
 15. Themethod of claim 10, wherein filtering the set of sub-blocks comprises:filtering the set of sub-blocks such that the left vertical edge and theright vertical edge of a bottom vertical neighbor sub-block is filteredbefore filtering a horizontal edge between a sub-block and the bottomvertical neighbor sub-block of the set of sub-blocks.
 16. The method ofclaim 10, wherein filtering the set of sub-blocks comprises: filteringthe set of sub-blocks such that filtering of any two edges of thesub-block is separated at least by one cycle of the de-blocking filter.17. The method of claim 10, wherein the macroblock is of a 16×16 pixelsize and the sub-block is of a 4×4 pixel size.